Signal deviation warning system



Oct. 20, 1953 J. E. TILLMN 2,656,527

SIGNAL DEVIATION WARNING SYSTEM WITNES SES INVENTOR:

Ilm

Oct. 20, 1953 J, E, MAN 2,656,527

SIGNAL DEVIATION WARNING SYSTEM Filed July 24, 1950 2 sheets-Sheet 2 Gain WITNESSES I i INVENTOR.'

Jgiln E. Tillman Patented Oct. 20, 1953 SIGNAL DEVIATION WARNING SYSTEM John E. Tillman, Albuquerque, N. Mex., assigner to v the United States of America as represented by the United States Atomic Energy Commission Application July 24, 1950, Serial No. 175,529

6 Claims.

This invention relates to a sensitive detection or protective system capable of giving an alarm or warning upon the entrance or intrusion of anybody into a particular area or zone protected by the system. The system employes a radiation iield of such directional characteristics and eX- tent as to encompass the particular area to be protected or the eld may be positioned to act as a barrier across any given opening such as a gate of a doorway or the like.

In recent years the need for sensitive, yet extremely reliable, protective or warning devices of the type referred to above has become extremely acute by reason of the need for maximum se" curity protection in connection with various types of buildings and installations where the intrusion of unauthorized personnel must be guarded against and prevented. The system of the present invention is one which establishes the barrier or protective screen in the form of a radiation eld produced by a transmitter and antenna transmitting a constant signal, the system embodying additional apparatus as will be described. Even a slight intrusion into the eld such as the throwing of an object into the field will produce a signal or alarm at a central alarm station. The system, of course, will give an alarm in the event of a person Walking into the field or a vehicle or the like intruding into the field. The presence of this detection system covering particular areas or zones or placed as a barrier across an entrance or the like is calculated to be unknown to intruders so that their presence can be detected before their being aware of it.

The system utilizes, in addition to the transmitter and antenna referred to above, a pair of similar antennas equally spaced from the transmitter antenna and connected to a receiver by coaxial lines which in terms of wave length of the transmitter are one-half wave length diierent in length; thus, if the receiving antennas are positioned and adjusted to receive signal at the same amplitude and phase, the signal will cancel. In practice the receiving antennas are adjusted so that there will be a certain amount of signal at the receiver for monitoring purposes. The result of this arrangement is that upon the intrusion of anybody into the radiation eld, as the result of re-radiation from the body to the receiving antennas, which re-radiation will be along paths of dierent length to the receiving antennas there will be a change of signal at the receiving end of the system which is detectable and can be made to trigger an alarm system giving warning of the entrance of the body into the eld.

In accordance with the foregoing the primary object of this invention is to provide a sensitive detection or warning system capable of giving a warning or signal upon the entrance or intrusion of anybody into a given protected zone or area. or through a gate or entrance or the like.

Another object of the invention is to provide a detection system as in the foregoing comprising a transmitting antenna setting up a radiation i'ield, a pair of similar antennas substantially equally spaced from the transmitting antenna in the eld and connected to a receiver by coaxial lines which are one-half wave length different in length in terms of wave length of the transmitter whereby any signal transmitted normally cancels at the receiver but re-radiated signals from anybody intruding into the eld produce a change in signal which is detectable at the receiver for purposes of triggering an alarm.

Another object of theAinvention is to provide a detection system as in the foregoing object wherein the receiver embodies a sensitive discriminator circuit for detecting a change in signal resulting from re-radiation embodying a normally balanced bridge circuit coupled to the receiver output so that any change in signal resulting from re-radiation unbalances the bridge, the unbalance of the bridge acting to trigger an alarm circuit.

Another object of the invention is an arrangement as in the foregoing object wherein the receiver output is coupled to the bridge as two opposite points and in such a way as to produce unbalance at both points which is cumulative with the result that the bridge circuit is extremely sensitive to any change in signal tending to produce unbalance.

Further objects and numerous advantages of the invention will become apparent from the following detailed description and annexed drawings wherein Figure l is a diagrammatic representation of the system showing the various antennas and an outline of the radiation eld.

Figure 2 is a wiring diagram of the circuit of the detector or discriminator circuit.

Figure 3 is a graph illustrating the voltage relationships across two of the legs of the bridge which vary in opposite directions upon changing signal.

Referring to Figure l of the drawings, numeral I designates a conventional radio transmitter coupled to an antenna 2 which produces a radiation eld having a pattern illustrated by the broken line 3 which represents the shape of the field in the horizontal plane. The radiation field is substantially cone shaped in both the horizontal and vertical planes.

Numeral 5 represents a radio receiver which is coupled to two receiving antennas 6 and 1 which, as shown are spaced at equal distances from the transmitting antenna 2 as indicated by the paths 9 and l0. The antennas 6 and 'l are coupled to the receiver 5 by coaxial lines |:2 and I3 which are diierent in length, as shown. by

the equipment. It can be seen, therefore, that the system is of extremely positive and reliable type in that there is no opportunity for the system to get out of order and become ineiective Without this being indicated to the operator at the control station and that during operation a disturbance of the radiation eld is indicated at the central station as an intrusion.

The foregoing is representative of a preferred form of my invention and it is intended that such variations and modications as may be made by those skilled in the art shall be covered by the claims appended hereto.

I claim:

1. In a discriminator circuit the combination of means forming a bridge circuit including a plurality of grid biased tubes having cathode resistors connected in opposing legs of the bridge, means including a signal input lead for coupling a signal input to the gri'ls of each of said tubes, blocking condensers connected with each of said grids and with said signal input lead, and rectiers connected with each of said grids and in shunt with each of said cathode resistors.

2. A circuit as claimed in claim l, in which said rectiers are so connected as to have opposite directional characteristics.

3. A circuit as claimed in claim 1, in Which a resistor is connected in each of said bridge legs and With the plates of said tubes.

4. A discriminator circuit comprising the combination of means forming a bridge circuit with a pair of electrically adjacent legs each including a thermionic tube with grid, plate and cathode and a resistor in series with the cathode, a signal input lead operatively connected with the grids of each of said tubes for coupling a signal input to said grids, condensers connected in series with each of said grids and with said signal input lead for coupling an input signal from the input lead to said grid and to rectiiiers, rectiers of opposite directional characteristics connected with each of said grids and with each other and with end portions of each of said cathode resistors remote from said cathodes, separate conductors and resistors connecting each of said tube plates with a power supply, a galvanorneter type meter connected between said separate conductors intermediate said resistors and the plates of said tubes, a plurality of relays having windings connected between said separate conductors and in parallel with said meter, and rectiers of opposite polarity connected in series with said relay windings to operate one relay on increase in signal and another relay on decrease in signal.

5. A circuit as claimed in claim 4, in Which potentiometers are provided in series with each of said relays for selectively setting the operating points of the relays.

6. A circuit as claimed in claim 4, in which leads are connected with contacts of each of said relays and are adapted to be connected with indicator means at a remote location.

JOI-IN E. TILLMAN.

References Cited in the le 0f this patent UNITED STATES PATENTS Number Name Date 2,038,878 Strutt Apr. 28, 1936 2,197,028 Wolff Apr. 16, 1940 2,206,923 Southworth J'uly 9, 1940 2,356,733 Banker Aug. 29, 1944 2,369,678 McWhirter et al. Feb. 20, 1945 2,440,283 Levy Apr. 27, 1948 2,498,103 Wojciechowski Feb. 2l, 1950 2,541,276 Oliver Feb. 13, 1951 

